import re
import os

from jedi import debug
from jedi.inference.cache import inference_state_method_cache
from jedi.inference.names import AbstractNameDefinition, ModuleName
from jedi.inference.filters import GlobalNameFilter, ParserTreeFilter, DictFilter, MergedFilter
from jedi.inference import compiled
from jedi.inference.base_value import TreeValue
from jedi.inference.names import SubModuleName
from jedi.inference.helpers import values_from_qualified_names
from jedi.inference.compiled import create_simple_object
from jedi.inference.base_value import ValueSet
from jedi.inference.context import ModuleContext


class _ModuleAttributeName(AbstractNameDefinition):
    """
    For module attributes like __file__, __str__ and so on.
    """
    api_type = u'instance'

    def __init__(self, parent_module, string_name, string_value=None):
        self.parent_context = parent_module
        self.string_name = string_name
        self._string_value = string_value

    def infer(self):
        if self._string_value is not None:
            s = self._string_value
            if self.parent_context.inference_state.environment.version_info.major == 2 \
                    and not isinstance(s, bytes):
                s = s.encode('utf-8')
            return ValueSet([
                create_simple_object(self.parent_context.inference_state, s)
            ])
        return compiled.get_string_value_set(self.parent_context.inference_state)


def iter_module_names(inference_state, paths):
    # Python modules/packages
    for n in inference_state.compiled_subprocess.list_module_names(paths):
        yield n

    for path in paths:
        try:
            dirs = os.listdir(path)
        except OSError:
            # The file might not exist or reading it might lead to an error.
            debug.warning("Not possible to list directory: %s", path)
            continue
        for name in dirs:
            # Namespaces
            if os.path.isdir(os.path.join(path, name)):
                # pycache is obviously not an interestin namespace. Also the
                # name must be a valid identifier.
                # TODO use str.isidentifier, once Python 2 is removed
                if name != '__pycache__' and not re.search(r'\W|^\d', name):
                    yield name
            # Stub files
            if name.endswith('.pyi'):
                if name != '__init__.pyi':
                    yield name[:-4]


class SubModuleDictMixin(object):
    @inference_state_method_cache()
    def sub_modules_dict(self):
        """
        Lists modules in the directory of this module (if this module is a
        package).
        """
        names = {}
        if self.is_package():
            mods = iter_module_names(self.inference_state, self.py__path__())
            for name in mods:
                # It's obviously a relative import to the current module.
                names[name] = SubModuleName(self.as_context(), name)

        # In the case of an import like `from x.` we don't need to
        # add all the variables, this is only about submodules.
        return names


class ModuleMixin(SubModuleDictMixin):
    _module_name_class = ModuleName

    def get_filters(self, origin_scope=None):
        yield MergedFilter(
            ParserTreeFilter(
                parent_context=self.as_context(),
                origin_scope=origin_scope
            ),
            GlobalNameFilter(self.as_context(), self.tree_node),
        )
        yield DictFilter(self.sub_modules_dict())
        yield DictFilter(self._module_attributes_dict())
        for star_filter in self.iter_star_filters():
            yield star_filter

    def py__class__(self):
        c, = values_from_qualified_names(self.inference_state, u'types', u'ModuleType')
        return c

    def is_module(self):
        return True

    def is_stub(self):
        return False

    @property
    @inference_state_method_cache()
    def name(self):
        return self._module_name_class(self, self._string_name)

    @property
    def _string_name(self):
        """ This is used for the goto functions. """
        # TODO It's ugly that we even use this, the name is usually well known
        # ahead so just pass it when create a ModuleValue.
        if self._path is None:
            return ''  # no path -> empty name
        else:
            sep = (re.escape(os.path.sep),) * 2
            r = re.search(r'([^%s]*?)(%s__init__)?(\.pyi?|\.so)?$' % sep, self._path)
            # Remove PEP 3149 names
            return re.sub(r'\.[a-z]+-\d{2}[mud]{0,3}$', '', r.group(1))

    @inference_state_method_cache()
    def _module_attributes_dict(self):
        names = ['__package__', '__doc__', '__name__']
        # All the additional module attributes are strings.
        dct = dict((n, _ModuleAttributeName(self, n)) for n in names)
        file = self.py__file__()
        if file is not None:
            dct['__file__'] = _ModuleAttributeName(self, '__file__', file)
        return dct

    def iter_star_filters(self):
        for star_module in self.star_imports():
            yield next(star_module.get_filters())

    # I'm not sure if the star import cache is really that effective anymore
    # with all the other really fast import caches. Recheck. Also we would need
    # to push the star imports into InferenceState.module_cache, if we reenable this.
    @inference_state_method_cache([])
    def star_imports(self):
        from jedi.inference.imports import Importer

        modules = []
        module_context = self.as_context()
        for i in self.tree_node.iter_imports():
            if i.is_star_import():
                new = Importer(
                    self.inference_state,
                    import_path=i.get_paths()[-1],
                    module_context=module_context,
                    level=i.level
                ).follow()

                for module in new:
                    if isinstance(module, ModuleValue):
                        modules += module.star_imports()
                modules += new
        return modules

    def get_qualified_names(self):
        """
        A module doesn't have a qualified name, but it's important to note that
        it's reachable and not `None`. With this information we can add
        qualified names on top for all value children.
        """
        return ()


class ModuleValue(ModuleMixin, TreeValue):
    api_type = u'module'

    def __init__(self, inference_state, module_node, code_lines, file_io=None,
                 string_names=None, is_package=False):
        super(ModuleValue, self).__init__(
            inference_state,
            parent_context=None,
            tree_node=module_node
        )
        self.file_io = file_io
        if file_io is None:
            self._path = None
        else:
            self._path = file_io.path
        self.string_names = string_names  # Optional[Tuple[str, ...]]
        self.code_lines = code_lines
        self._is_package = is_package

    def is_stub(self):
        if self._path is not None and self._path.endswith('.pyi'):
            # Currently this is the way how we identify stubs when e.g. goto is
            # used in them. This could be changed if stubs would be identified
            # sooner and used as StubModuleValue.
            return True
        return super(ModuleValue, self).is_stub()

    def py__name__(self):
        if self.string_names is None:
            return None
        return '.'.join(self.string_names)

    def py__file__(self):
        """
        In contrast to Python's __file__ can be None.
        """
        if self._path is None:
            return None

        return os.path.abspath(self._path)

    def is_package(self):
        return self._is_package

    def py__package__(self):
        if self._is_package:
            return self.string_names
        return self.string_names[:-1]

    def py__path__(self):
        """
        In case of a package, this returns Python's __path__ attribute, which
        is a list of paths (strings).
        Returns None if the module is not a package.
        """
        if not self._is_package:
            return None

        # A namespace package is typically auto generated and ~10 lines long.
        first_few_lines = ''.join(self.code_lines[:50])
        # these are strings that need to be used for namespace packages,
        # the first one is ``pkgutil``, the second ``pkg_resources``.
        options = ('declare_namespace(__name__)', 'extend_path(__path__')
        if options[0] in first_few_lines or options[1] in first_few_lines:
            # It is a namespace, now try to find the rest of the
            # modules on sys_path or whatever the search_path is.
            paths = set()
            for s in self.inference_state.get_sys_path():
                other = os.path.join(s, self.name.string_name)
                if os.path.isdir(other):
                    paths.add(other)
            if paths:
                return list(paths)
            # Nested namespace packages will not be supported. Nobody ever
            # asked for it and in Python 3 they are there without using all the
            # crap above.

        # Default to the of this file.
        file = self.py__file__()
        assert file is not None  # Shouldn't be a package in the first place.
        return [os.path.dirname(file)]

    def _as_context(self):
        return ModuleContext(self)

    def __repr__(self):
        return "<%s: %s@%s-%s is_stub=%s>" % (
            self.__class__.__name__, self._string_name,
            self.tree_node.start_pos[0], self.tree_node.end_pos[0],
            self.is_stub()
        )
